Primary support on Kent’s 380m long A20 Round Hill road tunnel uses different combinations of shotcrete, lattice arch girders and steel mesh reinforcement Across the UK and internationally, we've played a frontline role in the development of shotcrete lined tunnel schemes, leading the way to ensuring that this form of construction is appropriate and safe. Our hands-on experience has advanced our understanding of the system to the point where design and construction methods can be developed and fully justified prior to commencing work on site.

We employ state of the art analysis techniques in the design of shotcrete linings for arrangements including multiple tunnels and three dimensional junctions. These design methods are based on extensive empirical knowledge, calibrated against fully instrumented tunnels constructed in different ground conditions.

Research and development into shotcrete lined tunnels

Monitoring is an integral part of the construction of shotcrete lined tunnels, requiring a systematic approach to ensure that the information gained is both useful and economic. We’ve designed complete monitoring systems and developed software which provides graphical output to allow immediate confirmation that tunnel behaviour is within the specified design criteria. Teaming up with Surrey and Southampton Universities in the UK, we worked on a major research project looking at the use of pressure cells and other instrumentation in the monitoring of shotcrete lined tunnels.

On the UK Channel Tunnel, the shotcrete lined TBM erection chamber was constructed using NATM Risk is another factor critical to the construction process. We provide a full package of risk management from trained HAZOP engineers to the production of the risk assessments required in the new UK Construction Design and Management Regulations.

Mott MacDonald is the leader of a multi-disciplinary international team carrying out an EU funded Brite research project into fibre reinforced shotcrete. The team includes university departments as well as contractors which allows full-scale trials to be carried out.

Notable shotcrete lined tunnels designed by Mott MacDonald include:

• English Channel Tunnel, UK/France
• A20 Roundhill Tunnel, UK
• Singapore mass rapid transit
• CrossRail, London, UK
• Jubilee Line Extension, UK
• Heathrow Express Rail Link, UK
• Route 10, Hong Kong
• Mission Valley light rail transit, San Diego, USA
• A303 Stonehenge Tunnel, UK